Accident Eurocopter AS 332L2 Super Puma Mk2 G-WNSB, Friday 23 August 2013
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Date:Friday 23 August 2013
Time:18:17 LT
Type:Silhouette image of generic AS32 model; specific model in this crash may look slightly different    
Eurocopter AS 332L2 Super Puma Mk2
Owner/operator:CHC Scotia Ltd
Registration: G-WNSB
MSN: 2582
Year of manufacture:2002
Fatalities:Fatalities: 4 / Occupants: 18
Other fatalities:0
Aircraft damage: Destroyed
Location:off Fitful Head, 2 mi W of Sumburgh, Shetland Islands -   United Kingdom
Phase: Approach
Departure airport:Borgsten Dolphin MODU, North Sea
Destination airport:Sumburgh Airport, Shetland Islands (LSI/EGPB)
Investigating agency: AAIB
Confidence Rating: Accident investigation report completed and information captured
At 1717 hrs UTC on 23 August 2013, an AS332 L2 Super Puma helicopter with sixteen passengers and two crew on board crashed in the sea during the approach to land at Sumburgh Airport. Four of the passengers did not survive.

The purpose of the flight was to transport the passengers, who were employees of the UK offshore oil and gas industry, to Aberdeen. On the accident flight, the helicopter had departed the Borgsten Dolphin semi-submersible drilling platform in the North Sea, to route to Sumburgh Airport for a refuelling stop. It then planned to continue to Aberdeen Airport.

The commander was the Pilot Flying (PF) on the accident sector. The weather conditions were such that the final approach to Runway 09 at Sumburgh Airport was flown in cloud, requiring the approach to be made by sole reference to the helicopter’s instruments, in accordance with the Standard Operating Procedure (SOP) set out in the operator’s Operating Manual (OM). The approach was flown with the autopilot in 3-axes with Vertical Speed (V/S) mode, which required the commander to operate the collective pitch control manually to control the helicopter’s airspeed. The co-pilot was responsible for monitoring the helicopter’s vertical flightpath against the published approach vertical profile and for seeking the external visual references necessary to continue with the approach and landing. The procedures permitted the helicopter to descend to a height of 300 ft, the Minimum Descent Altitude (MDA) for the approach, at which point a level-off was required if visual references had not yet been acquired.

Although the approach vertical profile was maintained initially, insufficient collective pitch control input was applied by the commander to maintain the approach profile and the target approach airspeed of 80 kt. This resulted in insufficient engine power being provided and the helicopter’s airspeed reduced continuously during the final approach. Control of the flightpath was lost and the helicopter continued to descend below the MDA. During the latter stages of the approach the helicopter’s airspeed had decreased below 35 kt and a high rate of descent had developed.

The decreasing airspeed went unnoticed by the pilots until a very late stage, when the helicopter was in a critically low energy state. The commander’s attempt to recover the situation was unsuccessful and the helicopter struck the surface of the sea approximately 1.7 nm west of Sumburgh Airport. It rapidly filled with water and rolled inverted, but was kept afloat by the flotation bags which had deployed.

Search and Rescue (SAR) assets were dispatched to assist and the survivors were rescued by the Sumburgh-based SAR helicopters that attended the scene.

The investigation identified the following causal factors in the accident:
•The helicopter’s flight instruments were not monitored effectively during the latter stages of the non-precision instrument approach. This allowed the helicopter to enter a critically low energy state, from which recovery was not possible.

•Visual references had not been acquired by the Minimum Descent Altitude (MDA) and no effective action was taken to level the helicopter, as required by the operator’s procedure for an instrument approach.

The following contributory factors were identified:
•The operator’s SOP for this type of approach was not clearly defined and the pilots had not developed a shared, unambiguous understanding of how the approach was to be flown.

•The operator’s SOPs at the time did not optimise the use of the helicopter’s automated systems during a Non-Precision Approach.

•The decision to fly a 3-axes with V/S mode, decelerating approach in marginal weather conditions did not make optimum use of the helicopter’s automated systems and required closer monitoring of the instruments by the crew.

•Despite the poorer than forecast weather conditions at Sumburgh Airport, the commander had not altered his expectation of being able to land from a Non-Precision Approach.

On 19 June 2015 a Scottish Judge approved the release of the CVFDR to the Crown Office & Police Scotland.

Accident investigation:
Investigating agency: AAIB
Report number: 
Status: Investigation completed
Download report: Final report

Sources: (S6/2013) (S7/2013) (S1/2014)

Revision history:

23-Aug-2013 19:03 harro Added
23-Aug-2013 19:04 harro Updated [Location, Embed code]
23-Aug-2013 19:11 harro Updated [Time, Aircraft type, Operator, Embed code, Narrative]
23-Aug-2013 19:13 harro Updated [Time, Narrative]
23-Aug-2013 19:17 harro Updated [Location, Source]
23-Aug-2013 19:27 harro Updated [Aircraft type]
23-Aug-2013 19:39 harro Updated [Narrative]
23-Aug-2013 20:08 harro Updated [Narrative]
23-Aug-2013 20:26 Black Typhoon Updated [Time, Total fatalities, Other fatalities, Departure airport, Source]
24-Aug-2013 05:15 Geno Updated [Location, Phase, Nature, Departure airport, Destination airport, Source, Narrative]
24-Aug-2013 06:13 harro Updated [Location, Damage]
24-Aug-2013 07:25 harro Updated [Nature, Source]
24-Aug-2013 09:54 JoeF Updated [Total fatalities]
28-Aug-2013 07:27 Anon. Updated [Narrative]
28-Aug-2013 09:50 Anon. Updated [Registration]
29-Aug-2013 00:55 Dr.John Smith Updated [Cn, Operator, Source, Embed code, Narrative]
29-Aug-2013 04:20 Stringfellow Updated [Cn]
30-Aug-2013 08:19 harro Updated [Embed code, Narrative]
31-Aug-2013 20:10 Geno Updated [Source]
08-Sep-2013 08:22 qualityman Updated [Source]
26-Sep-2013 18:12 TB Updated [Location, Source, Narrative]
13-Oct-2013 07:45 MarkStep Updated [Source]
02-Aug-2014 17:20 Aerossurance Updated [Source, Narrative]
22-Aug-2014 09:48 Aerossurance Updated [Source]
20-Jun-2015 08:52 Aerossurance Updated [Source, Narrative]
21-Aug-2015 18:10 Aerossurance Updated [Source, Narrative]
25-Sep-2015 16:35 Dr. John Smith Updated [Operator, Source, Embed code]
02-Oct-2015 23:22 Dr. John Smith Updated [Embed code]
22-Dec-2015 11:54 Aerossurance Updated [Location, Narrative]
15-Mar-2016 14:21 Aerossurance Updated [Time, Departure airport, Source, Narrative]
25-Dec-2020 14:51 harro Updated [Nature]
24-Dec-2021 09:46 harro Updated [Accident report]
30-Jan-2024 19:08 Aerossurance Updated [Departure airport, Destination airport, Source]

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